In our country, the urban road pavement structure of highway is mainly asphalt pavement, which has a special characteristic of viscoelastic, causing both the properties of strength and flow to be affected by temperature. It brings in flat road surface, high driving comfort, low noise and small vibration, also, results in serious rut distress on the asphalt pavement structure due to repeated load of vehicle and the problem of surface cracking as an insufficient crack shrinkage or crack-resistance in low temperature of the semi-rigid base layer.
Though cement concrete pavement has the advantages of strong strength, good durability etc. and can effectively tackle the rutting problem, mud and dislocation are readily to emerge since its strong rigidity, complex arrangement of seam, high engineering cost, and inaccessibility for traffic during construction conservation, thus it cannot be preferably chosen as the anti-rutting pavement.
Observation and analysis on the rutting of asphalt pavement has been the focus of research at home and abroad. The early observations of rutting show that deformation is contributed mainly by the upper, middle layer, while the rutting occurs mainly on middle, lower layer in recent years and it occurs mainly at 5 cm below the road surface. However, this situation has not received due attention as a profound influence by the maximum shear stress theory. The maximum shear stress theory considers that the maximum shear stress in the middle layer is the main cause leading to rutting, and this rutting dominated by the middle, lower layer is perfectly matched with this theory. Tests show that the rut contribution rate (54.4%) of the semi-rigid base layer asphalt pavement lower layer is larger than that of the flexible pavement (26.6%), and it can be known that the rut contribution of the lower layer cannot be neglected under the circumstance of high temperature, heavy load and semi-rigid base layer. This is because that the very high temperature of the upper, middle layer during the heating process of the pavement leads to an naturally large lateral displacement, which will further aggravate plastic permanent deformation of the lower layer after yield; at the same time, it is naturally serious as the viscous flow of the structure layer and the higher temperature of the upper, middle layer; and the lower compressive stress of the lower layer naturally results in a small creep, rutting on the lower layer being mainly plastic deformation makes it have no recoverablility, causing a heavier damage.
According to the contradictory analysis of the philosophical thinking and the basic law of unity of opposites, it is required to invent a pavement structure, which combines the advantages of asphalt pavement and cement concrete pavement, has road flatness and sufficient bearing capacity, ensures an overall coordination of the pavement structure, overcomes shortcomings by learning from other's strong points, meets a good economic value and fast construction conservation period, and can be able to resist rutting deformation on the middle, lower layer against the conditions of semi-rigid base layer, high temperature, heavy load.